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California Enacts 4 New Laws to Promote Energy Storage

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California already leads the nation in energy storage deployments, but the legislature decided there was more to do on the policy end.

Governor Jerry Brown signed four bills into law Monday to further develop and streamline the state’s storage market. They direct the California Public Utilities Commission to evaluate the role large-scale storage can play for the integration of renewable energy, create an independent body to resolve storage interconnection disputes, expand funding for the Self-Generation Incentive Program by $249 million, and urge the state’s three investor-owned utilities to invest in up to 500 megawatts of storage projects on top of the existing 1,325-megawatt procurement target.

California has set a high bar for clean energy achievement. The state is pursuing 50 percent renewable energy by 2030, and aims to cut its greenhouse gas emissions to 40 percent below 1990 levels by 2030 as well. Reaching such high amounts of variable renewable generation all but requires a wider build-out of storage capacity to give the grid more control over when that wind and solar power is consumed. Whereas storage bills have languished in Congress, California’s leaders have demonstrated they know what storage can do and want to enlarge its role in the state.

“These four bills will accelerate the market opportunities for energy storage in California and give the state more options for how to use storage to meet the grid’s needs,” said Alex Morris, director of policy and regulatory affairs at the California Energy Storage Alliance.

With 73.2 megawatts of storage capacity, California has deployed more storage than any other single state. With that much in use, the state has a bounty of installations to analyze in order to refine the existing procedures. Other states are watching, so the optimization underway in this jurisdiction will set an example for younger storage markets.

In order for a storage market to thrive, developers have to have a simple and predictable way to connect newly deployed systems to the grid. Without strong interconnection standards, projects can get held up waiting for approval from the utility, which may then ask for large amounts of money if it deems the project will require upgrades to the surrounding grid infrastructure. 

Previously, if a developer took issue with the utilities’ assessment of costs to connect to the distribution grid, the avenues to address it were limited. The developer could go to an ombudsman who was paid by the utility, or shoulder the financial burden of going to court, Morris said.

Newly signed AB 2861 could change that. It authorizes the CPUC to create an independent dispute-resolution panel, staffed by electrical systems experts. Their job is to evaluate a disputed interconnection fee, gathering input from both sides and ruling on the case within 60 days.

This kind of contested outside evaluation should incentivize good behavior on both sides of the deal. That’s something other states can learn from as they endeavor to make the interconnection process smoother and cheaper.

AB 2868 is aimed at increasing the overall size of the storage market by directing utilities to deploy up to 500 megawatts of additional storage capacity, of which no more than a quarter can be behind-the-meter. New capacity from this program would be divided equally among the three big utilities. The law also directs the CPUC to prioritize projects for public-sector and low-income customers.

It’s not clear exactly how much an effect this law will have, given that the target is to “not exceed 500 megawatts.” The utilities can’t disobey an order from the legislature, delivered via the CPUC, but they could theoretically lowball it. Three megawatts of new storage, divided evenly among the big three IOUs, would not do a whole lot to modernize the California grid.

The real heft here might be the statement of intent: The legislature has declared its desire to see additional storage beyond what’s already been called for, and if the utilities fail to carry out the task in good faith they could face repercussions.

Speaking of statements of intent, AB 33 declares the legislature’s wish that the CPUC pay extra attention to long-duration storage for the grid. Deployments in recent years have been dominated by lithium-ion batteries, which work better for short-term use. To integrate renewables effectively, though, requires storing the energy from peak solar generation for several hours until the evening demand peak.

“The commission, in coordination with the Energy Commission, shall, as part of a new or existing proceeding, evaluate and analyze the potential for all types of long-duration bulk energy storage resources to help integrate renewable generation into the electrical grid,” the law says.

Now, it’s not like the CPUC was totally unaware of long-duration bulk storage. California already has 3,100 megawatts of pumped hydro storage, which is ideal for long-duration use. This bill simply elevates the significance of the topic to ensure it gets a little more attention going forward.

Lastly, the government let the money do the talking in AB 1637 by authorizing the CPUC to double the budget for the Self-Generation Incentive Program for the next three years. CESA says this adds $249 million to the pot for small-scale distributed energy resources, including storage.

The incentive program had come under fire initially when a couple of companies, including the carbon-emitting fuel-cell maker Bloom Energy, were able to monopolize most of the early disbursements. The CPUC has been retooling the program to democratize who gets the money, and to put most of the funding toward energy storage specifically.

Taken together, this set of laws indicates a maturing industry. The modern energy storage boom has been around enough for policymakers to think of things to improve that hadn’t occurred to them earlier — and to double down on things that are working.


Be the first to comment - What do you think?  Posted by Editor - September 30, 2016 at 6:01 am

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Does Your Commercial Rooftop Project Need a Dual-Axis Tracker?

This month, Edisun Microgrids launched the PV Booster dual-axis tracker solution for commercial and industrial (C&I) rooftops in advance of Solar Power International. 

With PV Booster, each rooftop PV module tracks the sun independently using an integrated light sensor, increasing energy production by an estimated 30 percent over a typical fixed-tilt system. While PV Booster adds to the balance-of-system (BOS) costs, about 25 percent fewer PV modules are needed to achieve the same annual energy output, thus lowering total installed system cost and reducing the levelized cost of electricity (LCOE) by some 20 percent. That’s what Edisun case studies say, at least.

Using an azimuth-altitude dual-axis tracking approach, PV Booster rotates east to west (azimuth) upon a ring attached to a ballasted rail matrix mounted on the rooftop. An arm behind the landscape-oriented module slides to adjust tilt above the horizon (altitude) up to 45 degrees. Although the azimuth-altitude’s low wind profile is the key enabler for PV Booster on rooftops, the rail matrix and azimuth ring require more rooftop square area per module than a fixed-tilt system.

On the first day of SPI, I happened upon the PV Booster booth, only to find Edisun Microgrids CEO and Idealab founder Bill Gross pitching the technology and product. After visiting the booth a few times and reviewing the case studies, I submitted the following questions to Edisun.

The question-and-answer format has been lightly edited for style and clarity.

Q: Why dual-axis instead of single-axis tracking?

Edisun: We use a full dual-axis tracker instead of single-axis to capture the maximum boost in annual power by adding the second axis.

The reason is because we have solved for the challenges posed by the wind. A single-axis tracker pivots the panels in the center so they can track east and west for early morning and late afternoon boost. However, that means the panel is up high in the wind stream, and would not be able to survive a rooftop-mount situation because of the torque-load placed on the roof.

On the ground, that’s easy since it’s solved by putting a pole deep into the ground. On the roof, that deep anchoring is not possible, and the roof is not strong enough to handle that. As for the second axis on the ground, if conventional trackers were to add the second axis it would have to move the massive structure altitudinally, and the economics would not pencil out.

We invented a new method of making a dual-axis tracker that pivots the panel from the front edge and not from the center. That means PV Booster captures the altitude changes of the sun, plus retracts the module to even lower on the roof than a stationary 10-degree rack. 

So, the second axis not only gives a boost in annual energy, but it makes the commercial rooftop trackers possible for the first time because we can retract completely flat in winds above 50 mph.

Q: How does PV Booster become bankable?

Edisun: PV Booster will be securing independent third-party engineering and performance verifications. For our first customers, we will work with a partner or provide direct project finance so that our customers will pay via PPA and not take any risk on our product.

Q: What is the PV Booster warranty? As a startup with a limited track record, how do you guarantee spares and qualified maintenance for 20-25 years?

Edisun: 10-year with extended warranty is available. We plan to back the warranty as needed with third-party warranty insurance.

Q: What is the basis for the operations and maintenance PV Booster delta of $7.5/kWp?

Edisun: We have put great engineering effort into creating O&M [practices] that [address] fixed-tilt. First, our system has fully distributed controls, so there is no single point of failure. Unlike other tracking systems that gang hundreds or sometimes even thousands of panels together, we have a separate microprocessor, sensor and controls for each PV panel. Out of a thousand panels, if one or two fail, then the other 998 will work perfectly and remain unaffected.

In addition, if two out of 1,000 fail, those two panels still produce power, just not with the 31 percent annual boost. Since our warranty covers that loss in energy production, there should be no O&M needed to fix those two units, because our warranty will pay out those funds.

To further increase reliability, we have eliminated the two things that fail the most in trackers — gearboxes and motor brushes. We designed a unique drive that is direct-drive (the only tracker in the world with no gearbox) and with brushless servo motors (no brushes to wear out). Our motors are rated for well over 1 billion cycles, which would represent thousands of years of PV Booster operation. The motors and mechanisms have been tested in harsh environmental chambers for more than 30+ years of lifetime with no failures. 

As a result, our testing shows that there will be minimal difference in O&M versus fixed-tilt. That said, in order to be conservative in our case studies, we added 50 percent to typical O&M costs as a reserve. 

Q: Is reliability data available? What failures have been observed during development?

Edisun: We have more than 1,000,000 tracking hours tested so far with no failures. We have not yet seen a mechanical, electrical or wear failure of any kind in all of our testing to date.

Q: I observed the cabling to be a potential point of failure.

Edisun: PV Booster’s cabling approach is similar to conventional fixed-tilt systems. Cabling and connector vendors are all UL approved.

The tracker movement flexes the cable bundle +/- 90 degrees once per day. We have run tests of more than 50 years of cable flexing with no wear or degradation, because we have a radius of curvature of the bundle that is well below the stress point of the wires. 

Q: From the case studies, the energy density of PV Booster per roof area is lower than fixed. What inputs do you have from local governments nationwide about added PV Booster design constraints for permitting?

Edisun: Our energy density on rooftops is approximately 33 percent less than more densely packed PV panels on fixed racks. However, we more than make up for that with the superior economics. Because of the spacing, we have a lighter load on rooftops of only about 2 pounds per square foot before ballast.

Our product must comply with the same PV standards (UL and ASCE in the U.S.) and must be installed to local building and fire codes, which we do.

Q: Does PV Booster stow itself flat if winds are excessive?

Edisun: Yes, PV Booster stows automatically when the wind is above 50 mph and has a backup system for doing so.

Q: How does PV Booster wake up in the morning?

Edisun: PV Booster wakes up automatically in the morning based on a light sensor in each unit that automatically detects when the morning light is sufficient. (These sensors keep each module optimally pointed at the sun all day.) 

Q: Is it grid-connected or does it begin operation when the morning sun is sufficient?

Edisun: PV Booster is grid-connected, but also has its own integrated [uninterruptible power supply] to continue tracking or to stow if the grid fails. In addition, if a tracker loses connectivity, it regresses to a stowed position until connectivity is restored. (Note that it would still produce as if it were a flat PV panel.)

PV Booster provides tangible cost savings to C&I customers subject to time-of-use electricity rates by generating more power during peak rate periods, especially at the end of the normal workday. However, C&I customers seeking to maximize rooftop megawatt-hour power generation regardless of timing might prefer to stick with a fixed-tilt system.

Going beyond the PV Booster case studies, I would recommend using higher efficiency monocrystalline PV modules and DC optimizers with PV Booster. Besides attracting dirt and debris, roofs are a favorite hangout for birds and their droppings.


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The Nordic Secret to Heavy-Vehicle Electrification: Old-Fashioned Cables

Europe’s Nordic countries are resorting to a technology from 1880 in a bid to solve one of the latest challenges in vehicle electrification.

Sweden and Norway are both building overhead power systems, similar to those used in electric trams dating back 136 years, in order to assist with the electrification of heavy-duty vehicles that are hard to move with existing battery technology alone. 

The current leader in overhead heavy-duty vehicle electrification is the Swedish truck maker Scania, which in June announced the opening of a two-kilometer e-highway in Gävle in mid-eastern Sweden.

Scania has adapted two of its G 360 4×2 hybrid trucks to draw power from overhead lines along the electrified stretch of the E16 motorway, a European highway that runs from Gävle in Sweden to Bergen in Norway and then, via ferry routes, to Scotland and Northern Ireland.

The trucks are equipped with a pantograph power collector mounted on the frame behind the cab, and can connect or disconnect freely from an overhead electric distribution system created by Siemens.

They operate as electric vehicles while on the electrified stretch of road, and as hybrid vehicles running on biofuel at other times. 

The e-highway, backed private and public sector bodies including the Swedish Transport Administration, Gävleborg Regional Authority, the Swedish Energy Agency Authority and research and development company Vinnova, is part of a two-year test. 

It is not clear if the concept will be extended across the country. In the meantime, however, neighboring Norway is making plans for highway electrification on a much grander scale.

The country, which already boasts the world’s most advanced electric vehicle market, is eyeing the outcome of the Swedish project to decide on how best to provide inductive charging for a 1,100-kilometer stretch of the E39, a highway running down western Norway to Denmark.

Officials are hoping to complete electrification of the route between Trondheim and Kristiansand by 2035, after launching a NOK 8 million (USD $1 million) pilot called “El in GO” last year.

According to reports earlier this year, officials have yet to decide on whether the technology will be overhead lines as in Sweden or an electrification system integrated into the road surface.

In any case, the plans being made by the Norwegian Roads Administration involve using renewable energy, including from solar, wind or wave generation, to help provide the estimated 1.5 terawatt-hours of electricity a year needed for full electrification of the route.

One of the challenges facing the project is how to provide electrification across the E39’s numerous bridges, including some that will replace existing ferry crossing and could be up to four or five kilometers long.

Nevertheless, Christina Bu, secretary general of the Norwegian EV Association, said the scheme would be a shot in the arm for Norway’s already advanced vehicle electrification program. 

“I think it is really good that there are initiatives that look into how we can cut emissions from heavy transport too, like the example in Sweden,” she said. “Heavy transport is the really big challenge ahead, as it is expected to grow a lot more than private transport.” 

Elsewhere, however, some have questioned whether tram-style electrification schemes are the right approach.

“Infrastructure investments move slowly and getting other automakers on board with a specific physical standard could be challenging,” said Colin McKerracher, manager for advanced transport insight at Bloomberg New Energy Finance. 

“Falling battery costs and improved energy density will make applications like on-board range-extenders more attractive over the coming years.”

An alternative approach that might prove more viable is the one being adopted by Tevva Motors, which combines battery power with a small diesel engine to allow “unlimited operational range,” according to the company’s website.

Tevva is currently testing the technology, which can be retrofitted to existing vehicles, in three trucks on U.K. roads.

Scania is also pushing ahead with standard hybrid trucks, although currently these have an electric range of up to 2 kilometers and are primarily being commercialized for use in situations where engine noise could be a problem. 


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Can Japan’s Energy Reforms Make Renewable Energy Growth Smarter?

Five years on, the Fukushima Daiichi nuclear power disaster is driving a restructuring of Japan’s $150 billion electricity sector. 

In April, the retail market opened to competition, representing a momentous shift for an industry where 10 regional power monopolies have long wielded outsized political influence to guard their interests. Over the years, Japan’s 80 million retail customers have endured some of the world’s highest energy prices.

Retail liberalization is the second phase of the Ministry of Economy, Trade and Industry’s (METI) plan to introduce competition throughout the electricity sector, following the creation of a market regulator in 2015.  Decoupling of generation and transmission holdings will come by 2020. 

Proponents hope that an open power market will lower prices and drive improvements to system reliability and stability. Both fell short in the wake of the 2011 reactor meltdowns that left the Tokyo area’s 20 million electricity customers short on power even as abundant supply existed elsewhere in the country. Tokyo is home to Tokyo Electric Power Company (TEPCO), Fukushima’s owner and Japan’s largest utility with 30 percent of end-user demand.

But challenges abound. “There are a couple of big risks to the success of these market reforms and retail competition,” said Charles Fahy, a power markets expert with PA Consulting Group in Wellington, New Zealand. “One is the lack of wholesale market liquidity and the other is the problem of transmission interconnections.”

Indeed, there are minimal bridges between the transmission networks, stifling aspirations for a truly national power market. Further complicating matters, the country’s electric grid operates on two frequencies: Japan’s west operates on 60 Hz, while the east, including Tokyo, is 50 Hz. The lack of interconnections was largely responsible for emergency conservation measures that forced TEPCO’s commercial power users to cut consumption by 15 percent to 20 percent despite excess capacity in the west.

The interconnection challenges, if not rectified, will limit the country’s ability to absorb intermittent renewable power — and to reap its benefits. 

“The Ministry’s policy goals following Fukushima were to secure stable supply, reduce electricity rates and enable choice for consumers and businesses, including encouragement of renewables,” said Fahy. 

After Fukushima, public backlash against nuclear power forced the country’s 50 nuclear power plants to shut down. Natural-gas generation, fueled by expensive LNG imports, grew from 30 percent to more than 40 percent of national electricity supply.

Looking to diversify its power base and cut emissions, the government introduced generous renewable feed-in tariffs.

“There was a huge uptake in PV, particularly ground-mounted installations over 10 kilowatts and residential,” said Fahy. “But the uptake was unbalanced. There wasn’t enough new wind, geothermal and biomass.”

The utilities became concerned with how to integrate the new intermittent resources. “Too much renewable power will cause system imbalances and issues with frequency control.”

Utilities covered the cost of the feed-in tariffs by raising retail rates an average 25 percent from 2012 to 2015. Subsequently, regulators looked to control costs. METI has since lowered the solar incentives, though at 24 cents per kilowatt-hour for 20 years they still look generous. Today renewables account for 4 percent to 5 percent of electricity supply, not counting hydro, which generates 10 percent of Japan’s power.

Looking forward, questions remain around the nascent energy market’s ability to incentivize a more diverse and clean grid. The wholesale market is undeniably weak. Less than 2 percent of generation is traded on the Japan Electric Power Exchange (JEPX) despite the fact that the wholesale market has been in operation since 2005. That means there’s little power available for the day-ahead and spot purchases that grease mature markets such as PJM Interconnection in the U.S. 

The Organization for Cross-Regional Coordination of Transmission Operators (OCCTO), the market regulator that came into being last year, has been charged with beefing up interconnections, which would give remote resources better access to big urban markets. 

“At the moment, the OCCTO is not operating as an independent system operator,” said Fahy. “System operations and dispatch responsibility falls to the legacy utilities who continue to control operation of their electric networks. It’s more of a governance and coordination body. There’s a bit of concern that it does not have enough authority to ensure that the interconnections that are needed are built.”

The old line utilities stand to maintain a significant de-facto presence despite deregulation. While generation and transmission assets will be decoupled by 2020, rules allow common ownership to continue through holding companies. In April, TEPCO restructured itself into a holding company with three operating units in retail, generation, and transmission and distribution.

In fact, there are few carrots to lure Japan’s legacy utilities to support efficiency or demand-side management measures that might erode revenues. The industry has explored decoupling, which is “going on around the fringes,” said PA’s Fahy. “There is government funding for grid edge technologies and virtual power plants, but it’s at an early stage.”

TEPCO, in particular, has good reason to protect its revenue stream. Since April, 300 or so retailers have appeared in the $72 billion retail market, stealing as many as 1 million customers from legacy providers. Sixty percent of retail switching has taken place in TEPCO’s footprint.

The electricity giant is countering with plans to expand the generation interests it already operates in other parts of Asia. Closer to home, it’s looking to offer retail power in other parts of Japan (though that may prove to be a zero-sum game) and to participate in natural-gas markets as that sector also opens to competition.

A potential bright spot for TEPCO lies in its plans to install 27 million smart meters by 2020. That would potentially leverage the information it collects to offer energy management solutions in the future. The utility is also developing distribution network control systems that would ease the future integration of renewables.

For its own part, the government has ambitions for a cleaner and more diverse grid by 2030. Natural gas will fall to 30 percent of the generation mix from 45 percent in the wake of Fukushima, while the country will re-certify its nuclear fleet. So far, three nuclear plants are back in operation. Renewables will account for up to a quarter of total generation, hydro included, up from about 14 percent today.

Will Japan’s reforms be enough to reach its clean energy goals? 

“In the long run, if interconnection issues aren’t eased, and access to wholesale markets isn’t enabled, it isn’t going to be successful in the eyes of consumers,” said Fahy.


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Wind Executive Worries About Competition From Cheap Solar: ‘It’s Quite Scary From Our Perspective’

Recharge: Solar a “Scary” Competitor to Wind in Growth Markets, Says Nordex CEO

Solar is becoming a “scary” competitor for the wind industry, particularly in many of the emerging markets that turbine suppliers are counting on for growth, said Nordex chief executive Lars Bondo Krogsgaard yesterday.

“One of the biggest challenges wind energy will have in the future is not coal or gas — increasingly we have to drive down our costs to match solar PV,” Krogsgaard said at the opening session of WindEurope Summit.

Speaking later to reporters, Krogsgaard added: “For the world, it’s a fantastic thing to have renewables technologies competing like this. But when you look at the way the cost curve is coming down [for PV], it’s quite a scary pace from our perspective.”

Forbes: Renault Beats Tesla and GM to the Punch With 250-Mile Range EV “Available Now”

There is one thing Tesla can be proud of: Automakers around the world are getting off their duffs. Today, French carmaker Renault announced at the Paris auto show that its fully electric “ZOE will be available for immediate sale with the Z.E. 40 battery enabling it to travel 400km NEDC.” The car is just one in a wave of longer-range EVs, launched by major automakers to compete with Tesla’s Model 3, which is not expected to appear in serious quantities before 2018.

RenewEconomy: Coalition Launches Fierce Attack Against Wind and Solar After Blackout

The Coalition government launched a ferocious attack against wind and solar energy after the major South Australian blackout, even though energy minister Josh Frydenberg and the grid operators admit that the source of energy had nothing to do with catastrophic outage.

Frydenberg, however, lined up with prime minister Malcolm Turnbull, deputy prime minister Barnaby Joyce, One Nation’s Malcolm Roberts, independent Senator Nick Xenophon and a host of conservative commentators, including Andrew Bolt, Alan Moran, the ABC’s Chris Ullmann, and Fairfax’ Brian Robins to exploit the blackout to question the use of renewable energy.

Frydenberg used the blackout to continue his persistent campaign against the renewable energy targets of state Labor governments in South Australia, Victoria and Queensland, saying that the blackout was proof that these targets were “unrealistic.”

PV Magazine: Solaria Files IP Lawsuit Against GCL Over Module Production Infringement

Solaria, the California-headquartered solar cell and module developer, is suing GCL Solar Energy – a subsidiary of China’s GCL-Poly Energy Holdings — over alleged misappropriation of trade secrets pertaining to the company’s module development techniques.

Solaria has filed a lawsuit against the Chinese firm for breaching the terms of a 2014 non-disclosure agreement signed by the parties. It is alleged that GCL Solar gained an unfair advantage in using Solaria’s patented techniques to produce their own shingled modules.

Tvo: Why Did the Liberals Backtrack on Their Renewable Energy Plan?

The Liberal government, which has emphasized its commitment to green energy, has publicly and loudly backpedaled on one part of that commitment, announcing it is nixing a planned second round of renewable energy procurement that would have added 1,000 megawatts of wind and solar power to the province’s grid.

The Liberals, still on the defensive about rising electricity costs, say foregoing the construction that would have been required to bring that new green energy on-line will save consumers $2.45 a month by 2032.

Minister of Energy Glenn Thibeault announced the reversal at Queen’s Park Tuesday morning, then followed up with a speech later that evening to the Ontario Energy Association, in which he stressed that the government wants to keep energy prices from growing even higher.


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Greenhouse Gases From Reservoirs Fuel Climate Change

Hydropower reservoirs are considered to be major sources of low-carbon electricity that can be used to cut greenhouse gas emissions to combat climate change. But those same reservoirs emit global warming gases, and a team of researchers has now tallied just how much those gases impact the climate.

Globally, reservoirs are responsible for about 1.3 percent of the world’s man-made greenhouse gas emissions each year, or about the same as Canada’s total emissions, according to a study to be published in the journal Bioscience next week. The findings come from a team of researchers led by Washington State University-Vancouver and the Environmental Protection Agency.

That emissions estimate may not sound like much, but the study says reservoir emissions can contribute significantly to carbon budgets countries use to meet their climate goals. Reservoirs emit mostly methane, a greenhouse gas about 35 times as potent as carbon dioxide in its potential to warm the atmosphere over the course of a century.

Lake Travis near Austin, Texas.
Credit: Bobby Magill/Climate Central

Knowing how reservoirs contribute to global warming is critical because there is a dam-building boom occurring worldwide. Previous research shows that about 3,700 major hydropower dams were planned or under construction globally as of 2014 as countries scramble to generate renewable energy and find new ways to store water during drought.

“To put these reservoir methane emissions in context, they are similar in size to other major human sources such as biomass burning and rice paddies, hence reservoirs are not necessarily the ‘clean’ energy source they are often thought to be,” the study’s lead authors, Washington State University-Vancouver Ph.D. student Bridget Deemer and environmental sciences professor John Harrison, said in an email.

The study’s greenhouse gas estimates include reservoirs built for all uses, including hydropower, drinking water, farm irrigation, and flood control, among others.

Reservoirs used for hydropower are often considered climate friendly because they are a renewable electricity source that does not burn fossil fuels. Most U.S. states include electricity generated at large hydropower dams as part of their strategy to use more renewables to cut greenhouse gas emissions and combat climate change.


Scientists have long known that reservoirs emit some greenhouse gases into the atmosphere because decomposing plant matter submerged under water releases methane, carbon dioxide and other gases. But until recently, scientists had too little data to estimate the total emissions from all the world’s reservoirs put together.

To do that, the research team synthesized the results of dozens of recent studies of more than 200 reservoirs across the globe, estimating that all the world’s reservoirs put together emit between 0.5 and 1.2 gigatons of carbon dioxide equivalents annually.

The study shows that reservoirs that grow more algae and other microbes tend to produce more greenhouse gases, and reservoirs in northern latitudes emit more methane than previously thought.

“While previous papers have found that young, tropical reservoirs emit more methane than older, more northern systems, our study finds that the total global warming effect of a reservoir is best predicted by how biologically productive it is, with more algae and nutrient rich systems producing more methane,” Deemer and Harrison said.

Amy Townsend-Small, an environmental science professor at the University of Cincinnati who is unaffiliated with the study, said mid-latitude reservoirs emit a lot of methane partly because a lot of fertilizer from farms washes into them, spurring algae blooms.

She called the study’s estimate of total global greenhouse gas emissions from reservoirs “encouraging.”

Colorado’s Lake Granby near Rocky Mountain National Park reached low levels in 2013.
Credit: Bobby Magill/Climate Central

“The single largest source of greenhouse gas emissions globally is electricity generation (about 25 percent of global greenhouse gas emissions), and that’s because fossil fuels are the dominant source of electric power,” Townsend-Small said. “Even though reservoirs emit methane and nitrous oxide, they still have an overall lower greenhouse gas footprint than burning coal for electricity.”

Michael Mann, an atmospheric scientist at Penn State University, said the study shows that building reservoirs makes a “very modest though not completely negligible” contribution to global greenhouse gas emissions.

“But I would note that, as the authors point out, most of this is methane, and that’s a relatively short-lived greenhouse gas compared to carbon dioxide,” Mann said. “So as far as the long-term committed warming is concerned, these emissions are of negligible significance.”

Kevin Trenberth, senior scientist at the National Center for Atmospheric Research, said the benefits of building reservoirs in an era of climate change can outweigh the impact of their methane emissions.

“Building reservoirs is essential if we are to manage water — to save the water from the heavier rains that occur for the longer dry spells that are also expected,” Trenberth said. “Water management is a huge issue and this study deals with only a tiny part.”

The study’s authors suggest that policymakers should weigh the global warming implications of reservoirs as they consider building new ones, but Townsend-Small said they still play a vital role in reducing emissions from fossil fuels.

“Hydroelectric reservoirs are still an important part of the global energy supply,” Townsend-Small said. “It makes sense to harness the energy supply contained behind dams in terms of electricity since the dam is also serving other purposes.”



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Energy Africa Conference

Wednesday, October 26, 2016 – 16:30 to Friday, October 28, 2016 – 16:30

Join the Clean Energy Solutions Center and its partners at the 9th Annual Energy Africa Conference. Attendees will include hundreds of executives, decision makers and thought leaders from the private sector, national governments, non-government organizations and academia from across the globe.


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New Mexico regulators OK electric rate hike

Concerns raised by environmentalists over the value of PNM’s stake in an Arizona nuclear plant spurred a recommendation over the summer that the multimillion-dollar request be slashed by two-thirds 


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After storm causes power outage, Australia debates clean energy

The state’s power operator, however, said the outage was unavoidable regardless of electricity sources


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Thailand’s Responsibility to the People of the Salween River

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